STORMWATER DRAINAGE ASSESSMENT. 479 Line 1 Road, Niagara-on-the-Lake, Ontario

Transcription

1 STORMWATER DRAINAGE ASSESSMENT 479 Line 1 Road, Niagara-on-the-Lake, Ontario November, Site Description Size: Location: Existing Land Use: Proposed Land Use: Soils: Stormwater Outlet: 1.38 hectares 479 Line 1 Road, Niagara-on-the-Lake, Ontario, Part of Lot 118, Geographic Township of Niagara, Town of Niagara-on-the-Lake, Region of Niagara Vacant agriculture Single Dwellings TVK-15 Tavistock cm reddish-hued loamy textures over clay loam till. Imperfect drainage (Ontario Institute of Pedology Field Mapping ). Existing 375mm dia. storm sewer on Harvest Drive, which eventually drains to Four Mile Creek. 2. Objectives The primary objectives of this assessment are to review the stormwater conveyance requirements (i.e. capacity) for the subject lands and to confirm the existing receiving stormwater conveyance system has sufficient capacity for the anticipated increased flows. 3. Stormwater Management Criteria a) Quantity Assessment: The existing 375mm diameter storm sewer on Harvest Drive currently does not accept flows from the project site. An assessment will be required to assess the capacity of the existing system and proposed development. b) Quality Control: The subject lands are tributary to Four Mile Creek which has been identified by the Ministry of Natural Resources as an Important (Type 2) fish habitat. Based upon this fish

2 Stormwater Drainage Assessment 479 Line 1 Road, Town of Niagara-on-the-Lake November, habitat, the corresponding Ministry of Environment level of protection required shall be Normal (Level 2) quality controls. c) Erosion Control: The subject lands will drain into the existing 375mm Harvest Dr. storm sewer, therefore, the provision for erosion control is not considered necessary. d) Impacts to Adjacent Lands: The subject area shall be self-contained and facilities for adjacent lands are not required, however, the overland drainage from some of the rear yards of existing residential homes surrounding the subject lands may be intercepted by the proposed storm sewer system. e) Siltation and Erosion Control: Siltation and erosion controls measures shall be implemented and maintained during the construction stage of this development, the engineering design drawings indicate the types of controls to be implemented, and shall include silt fencing along the boundary of the site, including straw bales at localized flow areas, and silt cloth over catch basins. 4. Stormwater Drainage Assessment a) Existing Conditions: The existing storm sewer system collects and conveys storm drainage from approximately hectares of developed lands north to Line 1 Road, where a storm sewer carries the flows to the east, ultimately outletting to Four Mile Creek. This existing storm sewer system was reviewed and a storm drainage design sheet (see Appendix A) was prepared to determine the existing stormwater capacity for the 5 year design storm event. Of particular interest in the assessment was the available capacity for the storm sewer section along Harvest Drive (from MH19 to MH20) as well as the section along Homestead Drive and Line 1 Road (MH 20 to Outlet), as the proposed works would only impact these existing sections of storm sewer. The existing areas upstream of these sewer sections (Area EX1) were consolidated into one drainage area utilizing the time of concentration calculated for the original storm sewer design. This analysis revealed that the above noted sections of the existing storm sewer system are only utilizing approximately 60% of their total available capacity. b) Proposed (Interim) Conditions:

3 Stormwater Drainage Assessment 479 Line 1 Road, Town of Niagara-on-the-Lake November, The proposed development will be undertaken in two phases. The first phase (interim) will consist of approximately 0.7 hectares with the proposed storm sewer system outletting to the existing storm sewer system to the east on Harvest Drive (MH19). In order to service this area, a 375mm storm sewer is proposed. A storm drainage design sheet (see Appendix A) for the 5 year storm is provided. The analysis confirmed that the existing storm sewer system has sufficient capacity to accommodate the increased flows from the development in the interim condition. However, the analysis did reveal that the receiving 375mm storm sewer along Harvest Drive (from MH19 to MH20) would be operating near capacity (approx. 95%) and would not be able to accommodate any additional flows from future developments. c) Proposed (Ultimate) Conditions: The second phase of the development will result in an additional 0.68 hectares of land being developed. As previously noted, the interim phase of development results in the storm sewer along Harvest Drive (from MH19 to MH20) operating near capacity. Therefore the second (ultimate) phase of this development cannot be constructed until sufficient (i.e. additional) capacity is provided. As detailed in the Town of Niagara-on-the-Lake Virgil Master Servicing Study, development that is to occur to the west will be constructed to accommodate the storm sewer flows from this development. Following the construction of this future storm sewer system, the second phase of this development can be implemented, with the interim connection at Harvest Drive (at MH19) either left in place or disconnected. d) Quality Improvements: As previously detailed, the existing stormwater conveyance system was constructed with excess capacity, and it can be assumed that this extends to excess capacity for quality control as well. As the existing storm drainage system would have been required to meet minimum quantity and quality impact levels to the receiving watercourse (i.e. Four Mile Creek), the increase in stormwater flows from this proposed development do not represent new impact to the receiving watercourse, rather, the proposed increase in flows has already been considered and accounted for in the original design and construction of the storm drainage system. Regardless, in the interim condition, an oil-grit separator, such as a stormceptor STC 300, should be utilized to provide suitable site specific quality control (i.e. >80% TSS reduction) to the stormwater flows prior to outletting to the existing storm sewer at MH 19. For the ultimate condition, stormwater quality improvements will be provided via the future stormwater pond as a part of the future development to the west.

4 Stormwater Drainage Assessment 479 Line 1 Road, Town of Niagara-on-the-Lake November, Conclusions Based on the assessment of the storm drainage, the following conclusions are provided: $ Stormwater flows from the first phase (i.e. interim) of this development can be accommodated utilizing the existing storm sewer system already in place. $ Adequate Quality Control for the interim phase can be achieved through the use of a suitably sized oil-grit separator. $ Stormwater flows from the second phase (i.e. ultimate) of this development require additional capacity, which is anticipated to be provided in the future development to the west. $ Quality Control for the ultimate phase will be provided via the future stormwater management facilities. All of which is respectively submitted, Stanley Pijl, P.Eng.

5 APPENDIX A

6 LINE 1 EX 900mmØ STM EX 900mmØ STM CHERRY STREET LEGEND EX 1350mmØ STM A A0 DRAINAGE AREA NUMBER DRAINAGE AREA IN HECTARES RUN-OFF COEFFICIENT DRAINAGE AREA BOUNDARY A STORMWATER OUTLET HENRY STREET EX6 GRANGE CRESCENT EX1 AUTUMN PLACE EX 375mmØ EX5 EX 900mmØ STM EX 900mmØ STM EX 525mmØ STM EX2 HOMESTEAD DRIVE FRONTIER DRIVE HEARTH CRESCENT HARVEST DRIVE EX 375mmØ STM EX 750mmØ STM EX4 EX3 PLANTATION DRIVE STM EX 675mmØ EX 450mmØ EX 525mmØ EX 525mmØ EX 450mmØ EX 450mmØ EX 375mmØ EX 375mmØ 375mmØ STM 375mmØ STM P2 P1 F1 479 LINE 1 ROAD STORM DRAINAGE AREA PLAN NIAGARA-ON-THE-LAKE, ONTARIO - STMDA

7 UPPER CANADA CONSULTANTS 261 MARTINDALE ROAD, UNIT 1 ST. CATHARINES, ONTARIO, L2W 1A1 RAINFALL PARAMETERS: A = mm/hr SEWER DESIGN: PIPE ROUGHNESS: FOR MANNING'S EQUATION 5 YEAR DESIGN STORM EVENT B = 4.70 minutes PIPE SIZES: ACTUAL DIAMETER SIZE FACTOR CITY OF ST. CATHARINES IDF C = PERCENT FULL: TOTAL PEAK FLOW / CAPACITY MUNICIPALITY: Town of Niagara-on-the-Lake PROJECT NAME: 479 Line 1 Road S T O R M S E W E R D E S I G N S H E E T PROJECT NO.: 1328 LOCATION STORMWATER ANALYSIS STORM SEWER DESIGN A R Time of Flow Rainfall Peak Nominal Full Flow Full Flow DESCRIPTION From To Area Runoff Accumulated Concentration Time Intensity Flow Length Diameter Slope Capacity Velocity Percent (hectares) Coeff. A*R A*R (min) (min.) (mm/hr) (L/s) (m) (mm.) (%) (L/s) (m/s) Full EXISTING CONDITION Harvest Drive (EX2) % Existing Development (EX1) Site Homestead Drive (EX3) % Homestead Drive (EX4) % Line 1 (EX5) % Line 1 (EX6) % Line 1 24 Outfall %

8 UPPER CANADA CONSULTANTS 261 MARTINDALE ROAD, UNIT 1 ST. CATHARINES, ONTARIO, L2W 1A1 RAINFALL PARAMETERS: A = mm/hr SEWER DESIGN: PIPE ROUGHNESS: FOR MANNING'S EQUATION 5 YEAR DESIGN STORM EVENT B = 4.70 minutes PIPE SIZES: ACTUAL DIAMETER SIZE FACTOR CITY OF ST. CATHARINES IDF C = PERCENT FULL: TOTAL PEAK FLOW / CAPACITY MUNICIPALITY: Town of Niagara-on-the-Lake PROJECT NAME: 479 Line 1 Road S T O R M S E W E R D E S I G N S H E E T PROJECT NO.: 1328 LOCATION STORMWATER ANALYSIS STORM SEWER DESIGN A R Time of Flow Rainfall Peak Nominal Full Flow Full Flow DESCRIPTION From To Area Runoff Accumulated Concentration Time Intensity Flow Length Diameter Slope Capacity Velocity Percent (hectares) Coeff. A*R A*R (min) (min.) (mm/hr) (L/s) (m) (mm.) (%) (L/s) (m/s) Full INTERIM CONDITION New Development (P1) P1 P % New Development (P2) P % Harvest Drive (EX2) % Existing Development (EX1) Site Homestead Drive (EX3) % Homestead Drive (EX4) % Line 1 (EX5) % Line 1 (EX6) % Line 1 24 Outfall %

9 UPPER CANADA CONSULTANTS 261 MARTINDALE ROAD, UNIT 1 ST. CATHARINES, ONTARIO, L2W 1A1 RAINFALL PARAMETERS: A = mm/hr SEWER DESIGN: PIPE ROUGHNESS: FOR MANNING'S EQUATION 5 YEAR DESIGN STORM EVENT B = 4.70 minutes PIPE SIZES: ACTUAL DIAMETER SIZE FACTOR CITY OF ST. CATHARINES IDF C = PERCENT FULL: TOTAL PEAK FLOW / CAPACITY MUNICIPALITY: Town of Niagara-on-the-Lake PROJECT NAME: 479 Line 1 Road S T O R M S E W E R D E S I G N S H E E T PROJECT NO.: 1328 LOCATION STORMWATER ANALYSIS STORM SEWER DESIGN A R Time of Flow Rainfall Peak Nominal Full Flow Full Flow DESCRIPTION From To Area Runoff Accumulated Concentration Time Intensity Flow Length Diameter Slope Capacity Velocity Percent (hectares) Coeff. A*R A*R (min) (min.) (mm/hr) (L/s) (m) (mm.) (%) (L/s) (m/s) Full ULTIMATE CONDITION Future Development (F1) F1 P % New Development (P1) P1 P %